If you want to reduce PDF file size using command line you can use ghostscript.Ghostscript is used for PostScript/PDF preview and printing. Usually as a back-end to a program such as ghostview, it can display PostScript and PDF documents in an X11 environment.
Furthermore, it can render PostScript and PDF files as graphics to be printed on non-PostScript printers. Supported printers include common dot-matrix, inkjet and laser models.

I just used Libreoffice 4.0 Draw to open the document and chose PRINT TO PDF to choose the resolution and quality percentage I needed. Adjust those settings to get it down to the size you require (without sacrificing quality too much of course).

Thanks! Reduced a 25MB pdf to 1.5MB! Quality OK.
This was a PDF created from an image file with ImageMagick’s convert command. Probably it could be used to directly reduce filesize, but I didn’t see that option.